phone boot up processs and cdp

Unanswered Question
Feb 4th, 2009

i've noticed that when we do packet capture on a phone booting up, its initial cdp advetisement, have a field in it stating Voip VLAN Query "vlan 512".

<br />Does anyone know if this is just a default vlan on the phone?

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gogasca Wed, 02/04/2009 - 22:48

For some reason, wireshark/ethereal interprets the value as 512, and I've never understood why. But it if you look at the actual data in the packet, the data is correct. Maybe 512 is 02 00 HEX...We dont have actually a default vlan inside but...

If a third gen phone has not received a Voice VLAN assignment from CDP, it will

advertise its Admin VLAN as a Voice VLAN on the PC Port. The phone should

never advertise its Admin VLAN as a Voice VLAN. If a Voice VLAN assignment has not been received from CDP, then the phone should not be advertising a Voice

VLAN on the PC Port.



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